Soil replacement for lawn

Hi all,

4 years ago I replaced the top 150mm of clay soil for my lawn with a loamy sand in order to improve drainage. At the same time 400mm deep drainage trenches were dug into the clay below at 2m intervals.

This totally sorted the drainage issue, but its gone too far the other way and now struggles to retain sufficient moisture or nutrients for healthy growth due to the low levels of silt and clay (I’ve had structural soil analysis carried out). The soil provided is actually a loamy sand, rather than the desired sandy clay loam, meaning it is very sandy indeed!

To remedy the situation I’m looking to replace the soil and am wondering whether I can get away with a 50/50 mix of new and existing by replacing just half of the loamy sand (75mm) with a more general purpose soil with higher levels of clay silt.

Or, whether I’m best off replacing the full 150mm with a soil that is already confirmed as having the desired proportions of sand / clay / silt.

My concern with a 50/50 mix is whether I’d be able to effectively combine the two to create a homogenous mix throughout the lawn. I don’t have any experience of rotivators, so not sure how effective they are in this respect.

Would love to hear if anyone has any experience of using a rotivator for this type of job.

Thanks

 

Hopefully some of our lawn experts will come in and help you.

However from your description it sounds like you have created a golf course green which like yours has trench drains and very sandy soil -
How To Build A Golf Course Green | Booth Golf & Leisure

Could it be that the grass is failing because with such free draining its not getting enough water and also not enough very frequent feeds?

If thats not the cause and you still want to replace the soil, would regular Top Dressings be an easier method, though taking much longer to be effective.

 

Hi Ricky 101, you’ve hit the nail on the head, the contractor has installed a blimmin golf green instead of a domestic lawn! Fine if you’ve got the time to be applying liquid feeds every few weeks and are irrigating all the time, but that’s not for me! I’m now looking to reinstate something more robust with a lower maintenance overhead.

I’m wondering if I should repost this message in the lawns section of the site?

 

Hi WKD, The lawn is 150 sq m, so I think I definitely need to be looking at a rotivator.

my plan is to either replace all of the new soil (top 150mm) or just half of this (75mm) and add new soil in.

Digging down to the clay sub base , at 150mm depth would be super hard work, and would interfere with the drainage channels too

 

Would love to do the work myself but I’ll most likely be looking for a landscaper to undertake the work and the excess soil will need to removed from site.

And the other main reason I don’t want to mix the clay sub base into the loamy sand on top is because it is almost 100% clay, which would result in too high levels of clay in the mix.

The optimum mix I’m aiming for is:

Sand (60–70%)
• Improves drainage and prevents waterlogging.
• Reduces compaction, allowing for deep root growth.

Silt (10–20%)
• Helps retain nutrients and moisture without making the soil too heavy.
• Adds some structure while still allowing air movement.

Clay (10–20%)
• Provides structure and holds essential nutrients.

• Too much clay causes compaction and poor drainage

 

Think we would try and let the worms and nature do the hard work for you.

If you use the soil of your choice to heavily topdress the lawn regularly over the growing season then it will be taken down into the sandy layers, which we would think will have settled down quiet a bit since it was made.

You could also look at hiring a Powered Hollow lawn Aerator and sweep the soil down into the holes.

You can add lawn seed to the dressing so you will in effect create a new lawn at the same time.

A tool like this seems to make speading the soil very easy and even.

 

I’ve looked into hollow coring but my soil is so sandy any holes made just collapse in on themselves. It just doesn’t have a rigid enough structure sadly.

and as much as I’d love Mother Nature to do the legwork, having endured a ropey lawn for the past 4 years I’m super keen to get it sorted asap to enjoy it this summer! The lawn maintenance company who came to inspect said it would take many years of top dressing to have a significant impact on the structure of the soil. I’ve added a pic of the soil analysis results and the sand content needs to be reduced from 82% to between 60 and 70% and the clay component upped from 2.3% to between 10 and 20% - which seems a lot of work from my resident worm community!

 

That really is a lot of sand. Budget permitting, I would pay a landscaper to remove the lawn and topsoil, dispose of both and replace with a suitable topsoil, at the correct depth, then seed or turf, without compromising your drainage system. Making sure that your landscaper fully understands your problem and your requirements should get the result you require.

My brother had a drainage problem with the lawn in the property he moved to a year ago. On excavating the lawn, the landscapers discovered that it had been laid on an added topsoil layer containing too much clay. Beneath it they found well draining sandy soil. They removed the clay topsoil, dug some drainage channels as a precaution and replaced the topsoil with a suitable mix. The lawn was replaced with new turf and is no longer a muddy mess in winter.

 

I think that’s the most likely route. Can you let me know what you think of retaining half the sandy topsoil and adding new with a lot more clay / silt?

I’ve found a soil supply which (at least on paper) would provide optimum proportions of sand / silt / clay when mixed 50/50 with mine

 

I don’t have the knowledge to advise you on that I’m afraid. A good landscaper (if you can find one) should be able to answer that and provide a guarantee for any work undertaken.

Another point to bear in mind is that you can buy different lawn seed mixes for different soils, situations and uses. I have a shaded, sandy lawn and use a mix from the Johnsons lawn seed range which performs well.

 

I have read the above posts and I must say that I am shocked !
I thought this forum was for gardeners.
The most critical ingredient in the mix is neither stated nor measured yet it surely is the answer that you seek.
HUMUS !
Your soil analysis does not show it at all!
"All good growing needs a shower each day- and a shower of ***t on Sunday" (A G Street?)

 

The report posted is solely mechanical properties, or structural analysis, so just from a purely physical perspective. Organic matter was actually within acceptable parameters when I had it tested with a standard test. Took me a long time to work out my problem is with the soil’s inherent properties, that you can’t do much about with either feeding or the addition of organic material

 

no probs, and the reason for canvassing opinion here and the deep dive I’m taking is the original landscaper who specialised in lawns and drainage gave me a bad steer with the soil. So it’s a case of once bitten twice shy!